As I understand it, they can't fit two antiwarp walls on a page and have them both fit between the guidelines used by the robocutters, so that's why you always have one regular and one antiwarp on a page. At least I think it was something like that. I could be mistaken.
Whether or not to use the regular walls is a very individual decision. Some people say they use the antiwarp walls for all the outside walls and the regular walls for interiors.
I pretty much use the antiwarp walls exclusively, only using the regular walls when I run out of antiwarps. For the Thoumonts TLX set, I created a page of antiwarp triangles and use them to convert the regular walls to antiwarp, though I had to play with my printer's reduction settings to get them to print out the right size (darn GIMP anyway!).
Hope that answers your question. I'm sure the more experienced members of the forums will have some more detailed advice on the issue.
EDIT: Ooooh, ninja'd by Matthew777. I bow to your swifter power, good Sir.
